Mineral Transition of Calcium Aluminate Clinker during High-Temperature Sintering with Low-lime Dosage

摘要

The mineral transition mechanism and physicochemical property of calcium aluminate clinker sintered at 1350 ℃ were systematically studied using analytical reagent α-Al_2O_3,CaCO_3 and SiO_2 when the molar ratio of CaO to Al_2O_3 is 1.0.The results show that the formation of Ca_2SiO_4 accelerates the diffusion of CaO and Al_2O_3,which promotes the formation of CaAl_2O_4 determined by dilatometer,X-ray diffraction,Fourier transform infrared spectroscopy and scanning electron microscopy methods.CaAl_4O_7,Ca_3Al_2O_6,Ca_3SiO_5 and Ca_2Al_2SiO_7 only exist in the initial stage of reactions,the amounts of which decrease with the increase of sintering duration.Ca_3Al_2O_6 and Ca_(12)Al_(14)O_(33) react with Al_2O_3 and CaAl_4O_7 to form CaAl_2O_4,while Ca_2Al_2SiO_7 reacts with CaO and Ca_(12)Al_(14)O_(33) to form Ca_2SiO_4 and CaAl_2O_4.The sintered clinker contains CaAl_2O_4 and γ-Ca_2SiO_4 as well as some Ca_(12)Al_(14)O_(33) when the sintering duration is longer than 1.0 h.The differential scanning calorimetry results reveal that Ca_2SiO_4,Ca_2Al_2SiO_7 and CaAl_2O_4 are formed at985 ℃,1045℃ and 1339 ℃,respectively.Increasing the sintering duration contributes to the transition of β-Ca_2SiO_4 to γ-Ca_2SiO_4,which improves the pulverization and alumina leaching property of the sintered clinker.